Isochronous data is defined as time dependent data that must be delivered within certain time constraints, but unlike synchronous data, need not be delivered only at specific intervals. In addition, isochronous data is unlike asynchronous data which can be transmitted at random intervals. Moreover, isochronous software applications may send isochronous data to and from sensors and transducers, such as video displays, video cameras, audio microphones, audio speakers, and data repositories or sources such as a memory modules. For example, multimedia streams may require an isochronous transport mechanism to insure that video data is delivered fast enough to enable each frame to be displayed at its associated render time. The isochronous transport mechanism may insure that audio data is delivered within time constraints necessary to prevent buffer under-runs and audible errors at the codec and speakers. Therefore, isochronous applications for transmitting isochronous data to and from isochronous devices require guaranteed bandwidth and deterministic latency between the isochronous transmitting and receiving devices
In a power managed profile of a digital electronic system, support of isochronous applications may require more power than support of interrupt driven activity such as asynchronous applications or activity initiated asynchronously. For example, a laptop computer or a handheld device using battery power may be unable to support a power managed profile to maximize battery life and provide adequate isochronous communications for its isochronous devices. Specifically, the laptop computer or handheld device may exceed the power managed profile when powering components (e.g., such as a processor, memory, processor logic and memory controller, chipset logic for handling device, data communication bus, and the isochronous device) as necessary to provide the required guaranteed bandwidth and deterministic latency for transmitting isochronous data within the time constraints required by the isochronous devices.